Effect of Moisture on the Strength of a Clean Sand

Fully-drained triaxial compression tests on samples of a clean river sand (Antioch sand) indicated that the soil was considerably stronger in the oven dry than in the saturated state. The strength of air dry sand was intermediate between these two extremes. The decrease in strength with increasing moisture content was accompanied by a decrease in the dilatant volume change tendency, and by an increase in particle crushing as the samples were sheared. A few special sustained loading tests were performed on air dry and oven dry samples of this sand. The sustained loads were less than the air dry strength, but greater than the strength when saturated. Both air dry and oven dry samples failed almost immediately after water was introduced through a drainage line at the base. Microscopic analysis of this sand indicated that some of the particles appeared to be weathered and cracked, and some of the cracks may have contained thin films of clay. The peculiar water sensitive behavior of this sand was attributed to the presence of these cracks in some of the particles.